The field of the disclosure relates generally to components having an internal passage defined therein, and more particularly to systems and methods for sealing internal channels defined in a component.
Some components require an internal passage to be defined therein, for example, in order to perform an intended function. For example, but not by way of limitation, some components, such as hot gas path components of gas turbines, are subjected to high temperatures. At least some such components have internal passages defined therein to receive a flow of a cooling fluid, such that the components are better able to withstand the high temperatures. For another example, but not by way of limitation, some components are subjected to friction at an interface with another component. At least some such components have internal passages defined therein to receive a flow of a lubricant to facilitate reducing the friction.
At least some known components having an internal passage defined therein are formed in a mold, with a core of ceramic material extending within the mold cavity. After a molten metal alloy is introduced into the mold cavity around the ceramic core and cooled to form the component, the ceramic core is removed, such as by chemical leaching, to form a preliminary internal passage. Alternatively or additionally, at least some known components having an internal passage defined therein are initially formed without the internal passage, and the internal passage is formed in a subsequent process. For example, at least some known internal passages are formed by drilling the preliminary passage into the component, such as, but not limited to, using an electrochemical drilling process.
Moreover, for at least some known components, it is necessary to form an internal closure within the preliminary internal passage in order to produce a selected final configuration of the internal passage. For example, but not by way of limitation, the preliminary internal passage as formed passes through an outer wall of the component to simplify the forming process, and the internal passage must be sealed interiorly of the outer wall to properly define the selected final configuration. Additionally or alternatively, as another non-limiting example, the internal passage is part of a network of internal passages defined within the component, and the internal closure is necessary to produce a selected flow pattern through the network of internal passages. One known method of forming such internal closures is to insert a metallic closure element within the passage at the selected closure location, and to couple the closure element to the passage walls using, for example, a braze joint to create a seal. However, for at least some such components, a small diameter of the internal passage reduces or eliminates an ability to effectively clean or remove contamination from the closure site. Occasionally, due for example to contamination, incomplete cleaning, or effects of leaching out the ceramic core at the closure site, local defects occur in the joint, resulting in an incomplete seal and an ineffective closure. Moreover, while some such defects are repairable using, for example, multiple brazing cycles, at least some such defects may be incurable through brazing, potentially resulting in an unusable component.